A group of Taliban militants strapped with explosives and armed with rifles and rocket-propelled grenades launched assaults Tuesday on Afghan and U.S. facilities in two eastern Afghan cities, killing six security officers.

Officials say the gunmen, some wearing suicide vests and disguised in women's burqa robes, tried to storm the local intelligence office, the governor's office and a police compound in Gardez, the capital of Paktia province. Six militants were reported killed in gunbattles with police.

In Jalalabad, the capital of northeastern Nangarhar province bordering Pakistan, at least two militants were killed while trying to attack a base for U.S. and Afghan forces.

A Taliban spokesman, Zabihullah Mujahid, claimed responsibility for the attacks. He said 15 suicide bombers took part in the Gardez assault.

In other violence Tuesday, 13 Taliban were killed and 12 wounded during an operation in northern Kunduz province. Five Afghan soldiers also were killed in the fighting.

Another 10 Taliban militants were killed Monday night when a bomb they were making exploded in a house in central Ghazni province.

And, the U.S. military said Tuesday an American soldier was killed in a vehicle accident near the capital, Kabul.

Meanwhile, NATO's outgoing secretary-general, Jaap de Hoop Scheffer, has said the alliance's mission in Afghanistan is essential to international security.

De Hoop Scheffer said that if Afghanistan fell to the Taliban, extremism would spread and al-Qaida would have a free hand to expand its global terrorist ambitions.

He added that NATO has made progress, but faces challenges in the 21st century and must adapt to the modern world.